Back in the 1980’s, a now-defunct magazine called Science Digest held a contest to name Planet X — the still-undiscovered world that astronomers believed might lie out beyond Pluto. One of the best entries, sent in by a school child: Goofy, suggested on the theory that one planet named after a Disney cartoon dog deserved another. (Another suggestion, Plutus, lacked a certain originality.)

Fortunately, the magazine’s choice had no official weight, and in the end, astronomers abandoned their idea of a Planet X altogether. In 2006, Pluto itself, as we know, was demoted to the status of “dwarf planet” (a move that had been in the works for 50 years, as this vintage Time story illustrates). But while poor Pluto has lost some status in the overall rankings, it keeps moving up in the “Who Has the Most Moons” list. Last July, the HubbleSpace Telescope spotted a new one, bringing Pluto’s tally up to five — which is two more than Mercury, Venus, Earth and Mars have, combined.

Three of Pluto’s moons have been named (they’re Charon, Nix and Hydra). But two remain nameless— they’re simply known as P4 and P5 — and now the SETI Institute is sponsoring a contest to remedy that situation. Anyone who goes to http://plutorocks.seti.org can either pick from a list of names suggested by the moons’ discoverers or write in entirely different suggestions.

It feels like a novel idea (Science Digest notwithstanding), but in fact, the tradition goes all the way back to Pluto’s discovery in 1930. That happened at Lowell Observatory in Arizona, and when the news that a new planet had been found got out, suggestions poured in for what to call it. (Constance Lowell, widow of the observatory’s founder, helpfully proposed several ideas, including “Constance”).

In the end a British schoolgirl named Venetia Burney came in with the winner. All of the other planets (except Earth) were named for Classical gods, and Burney, reasoning that this distant new world was cold and dark, proposed naming it after the Roman god of the underworld.

This was long before the International Astronomical Union came up with its formal guidelines for naming celestial objects. These rules can get pretty arcane when it comes to moons. For example, newly discovered satellites of Saturn (which has 53 and counting) must be named for “Greco-Roman titans, descendents of titans, the Roman god of the beginning, and giants from Greco-Roman and other mythologies.” For Uranus (27 so far) it’s “characters from Shakespeare’s plays and from Pope’s ‘Rape of the Lock’.” (The rules don’t always produce the most dignified results. Moon number 20, Stephano, is named for a drunken butler in The Tempest).

But for Pluto, there’s no official rule. The SETI folks running the contest note that “by tradition, the names of Pluto’s moons come from Greek and Roman mythology, and are related to the ancient tales about Hades and the underworld.” Even if it’s just a tradition, however, and not a rule, it’s pretty unlikely the judges, which include Mark Showalter of the SETI Institute plus the scientists who discovered P4 and P5, will overstep those bounds.

Anyone voting for Constance, or Snooki, or a character from South Park, in short, is almost certainly not going to win.